Around 1 lakh for a decent trip which will include airfare , say , food and sight seeing . Usually flight cost to Bali are high as they is no direct flight from India . Rest other can be managed in reasonable budget
A trip to Bali with round tickets may cost you around 45-70k depending upon how early you book your flight tickets, this is including approximate overhead cost in Bali. Flight tickets 30-50k depending upon how early you book them. Visa on arrival for Indians $35 Hotels are cheap considering ₹ is stronger in Bali. Good Scooties can be rented for as cheap as ₹300-500 per day. But during the stay in Bali you may find food is little expensive and shopping places as well. P. S. It is easy to bargain there at prices so as to cut down the prices.
There is direct flight to bali from Mumbai named as garuda airways.. it would cost near to 1 lakh if u include the flight price. check hostels in bookings.com.. for transportatn dont use cabs, rent a scooter.. u cn cover gilli island in those 7 days too.. u can cover most of bali in 5 days i guess...stay in ubud for 2 days and then 3 days in sanur.. if u stay in sanur u cn book a ferry to nusa penida island easily or u cn stay in Denpasar for the airport.. its your choice.